Kepler-88 d
Astrophysical Synthesis & Habitability Characterization
Kepler-88 d is a confirmed gas giant exoplanet orbiting the star KOI-142, located approximately 1229.2 light-years (376.86 parsecs) from the Solar System. First announced in 2020 by W. M. Keck Observatory using the Radial Velocity detection technique (measuring periodic Doppler reflex motion in the host star's spectrum), this world measures 13.1 Earth radii (1.17 Jupiter radii) and has a measured mass of 965.147 Earth masses (3.04 Jupiter masses). Combining its mass and radius yields a mean bulk density of 2.37 g/cm³ (an intermediate density indicative of a deep water-ice mantle or dense volatile envelope), a surface gravity of 5.62 g⊕ (55.11 m/s²), and an escape velocity of 96 km/s.
In its orbital architecture around KOI-142, Kepler-88 d completes one full revolution every 1403 Earth days (3.84Julian years) at a semi-major axis of 2.46633 AU (corresponding to the middle-system regime between Mars at 1.52 AU and Jupiter at 5.20 AU). Its mean orbital velocity is approximately 19.1 km/s (compared to Earth's 29.8 km/s). The planet follows a highly eccentric trajectory (e = 0.41, swinging from 1.4551 AU at periapsis out to 3.4775 AU at apoapsis), pointing to past dynamical scattering or secular gravitational perturbations.
❄️ Thermal Regime (Cryogenic Zone): With an equilibrium temperature of 159 K (-114°C / -173°F) and an incident flux of 0.11 S⊕ (~153 W/m²), surface water and volatile species on Kepler-88 d would remain locked in cryogenic ice phases unless warmed by subsurface tidal or radiogenic heating.
The host star KOI-142 is classified as a solar-type yellow star of spectral type G with an effective photospheric temperature of 5,466 K, a radius of 0.897 R☉, a mass of 0.99 M☉, an estimated bolometric luminosity of 0.644 L☉. Stellar evolution modeling indicates an estimated stellar age of 1.6 Gyr and a metallicity of [Fe/H] = 0.27 dex (metal-rich relative to the Sun). From Earth, KOI-142 shines at apparent V-band magnitude 13.209 (faint and requiring research-grade or CCD telescopic photometry) in the Northern celestial hemisphere. The KOI-142 system is a multi-planet architecture hosting 3 confirmed worlds, with Kepler-88 d sharing its stellar neighborhood alongside KOI-142 b, KOI-142 c.
Methodology: Computed using the Schulze-Makuch et al. (2011) weighted metric comparing physical interior (radius, estimated density) and surface thermal regime (escape velocity, equilibrium temperature).
Discovery Facility: W. M. Keck Observatory · Catalogue Source: NASA Exoplanet Archive (IPAC / Caltech).
☀️ Host Star Telemetry
| Host Star Name | KOI-142 |
| Spectral Type | G |
| Effective Temp (Teff) | 5,466 K |
| Stellar Radius | 0.8970 R☉ |
| Stellar Mass | 0.9900 M☉ |
| Bolometric Luminosity | 0.644 L☉ |
| Metallicity [Fe/H] | 0.270 dex |
| Stellar Age | 1.600 Gyr |
| Apparent Magnitude | V: 13.209 · G: 13.105 |
| System Architecture | 1 Star, 3 Planets |
🪐 Orbital & Physical Dynamics
| Semi-Major Axis (a) | 2.466330 AU |
| Orbital Period | 1403 days |
| Mean Orbital Velocity | 19.1 km/s |
| Orbital Eccentricity (e) | 0.41000 |
| Orbital Inclination (i) | 89.0000° |
| Mean Bulk Density | 2.37 g/cm³ (96 km/s vesc) |
| Insolation Flux | 0.1124 S⊕ (~153 W/m²) |
| Habitable Zone Status | Exterior / Non-HZ |
| Celestial Distance | 1229.200 LY (376.863 pc) |